Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
h, w = map(int, input().split())
s = [list('#' * (w + 2))]
queue = [[1, 1, 1]]
dot = 0
for i in range(h):
    s.append(['#'] + list(input()) + ['#'])
    dot += s[-1].count('.')
s.append(list('#' * (w + 2)))

def move(yxc):
    y, x, cost = yxc[0], yxc[1], yxc[2]
    global queue
    for dy, dx in ([1, 0], [-1, 0], [0, 1], [0, -1]):
        ny, nx = y + dy, x + dx
        if s[ny][nx] == '.':
            s[ny][nx] = cost + 1
            queue.append([ny, nx, cost + 1])

while len(queue) > 0:
    move(queue.pop(0))

s[1][1] = 1
move([1, 1, 1])
if s[h][w] == '.':
    print(-1)
else:
    print(dot - s[h][w])